Retroviruses
Retroviruses are small, single-stranded positive-sense RNA viruses. A retroviral particle comprises two identical single-stranded positive sense RNA molecules. Their genome contains, among other things, the sequence for the RNA-dependent DNA polymerase, also known as reverse transcriptase. Many molecules of reverse transcriptase are found in close association with the genomic RNA in the mature viral particle. Upon entering a cell, this reverse transcriptase produces a double-stranded DNA copy of the viral genome, which is inserted into the host cell's chromatin. Once inserted, the viral sequence is called a provirus. Retroviral integration is directly dependent upon viral proteins. Linear viral DNA termini (the LTRs) are the immediate precursors to the integrated proviral DNA. There is a characteristic duplication of short stretches of the hosts DNA at the site of integration.
Progeny viral genomes and mRNAs are transcribed from the inserted proviral sequence by host cell RNA polymerase II in response to transcriptional, regulatory signals in the terminal regions of the proviral sequence, the long terminal repeats or LTRs. The host cell's proteins production machinery is used to produce viral proteins, many of which are inactive until processed by virally encoded proteases. Typically, progeny viral particles bud from the cell surface in a non-lytic manner. Retroviral infection does not necessarily interfere with the normal life cycle of an infected cell or organism. However, neither is it always benign with respect to the host organism. While most classes of DNA viruses can be implicated in tumorigenesis, retroviruses are the only taxonomic group of RNA viruses that are oncogenic. Various retroviruses, such as the Human Immunodeficiency Virus (HIV), which is the etiological agent responsible for acquired immune deficiency syndrome (AIDS) in humans, are also responsible for several very unusual diseases of the immune systems of higher animals.
HIV INFECTION AND AIDS
Human Immunodeficiency Virus (HIV), the etiological agent for AIDS (acquired immune deficiency syndrome), is a member of the lentiviruses, a subfamily of retroviruses. Many retroviruses are well-known carcinogens. HIV per se is not known to cause cancer in humans or other animals, but it does present a formidable challenge to the host. HIV integrates its genetic information into the genome of the host. The viral genome contains many regulatory elements which allow the virus to control its rate of replication in both resting and dividing cells. Most importantly, HIV infects and invades cells of the immune system; it breaks down the body's immune system and renders the patient susceptible to opportunistic infections and neoplasms. The immune defect appears to be progressive and irreversible, with a high mortality rate that approaches 100% over several years.
HIV-1 is trophic and cytopathic for T4 lymphocytes, cells of the immune system which express the cell surface differentiation antigen CD4 (also known as OKT4, T4 and leu3). The viral tropism is due to the interactions between the viral envelope glycoprotein, gp120, and the cell-surface CD4 molecules (Dalgleish, et al., Nature 312:763-767, 1984. These interactions not only mediate the infection of susceptible cells by HIV, but are also responsible for the virus-induced fusion of infected and uninfected T cells. This cell fusion results in the formation of giant multinucleated syncytia, cell death, and progressive depletion of CD4 cells in AIDS patients. These events result in HIV-induced immunosuppression and its subsequent sequelae, opportunistic infections and neoplasms.
In addition to CD4+T cells, the host range of HIV includes cells of the mononuclear phagocytic lineage (Dalgleish et al., supra), including blood monocytes, tissue macrophages, Langerhans cells of the skin and dendritic reticulum cells within lymph nodes. HIV is also neurotropic, capable of infecting monocytes and macrophages in the central nervous system causing severe neurologic damage. Macrophage/monocytes are a major reservoir of HIV. They can interact and fuse with CD4-bearing T cells, causing T cell depletion and thus contributing to the pathogenesis of AIDS.
ANTI-HIV DRUGS
Intensive efforts are currently under way to develop therapies to prevent or intervene in the development of clinical symptoms in HIV-infected individuals. For the most part, efforts have been focused on the use of nucleoside analogue drugs such as AZT (azidothymidine), and on other dideoxynucleoside derivatives such as ddA, ddT, ddI, and ddC. These drugs inhibit the viral enzyme, reverse transcriptase, thereby inhibiting de novo infection of cells. However, once viral infection has been established within a cell, viral replication utilizes host cell enzymes. Thus, drugs which inhibit only reverse transcriptase tend to have limited effects. While the spread of free virus within the organism can be blocked, the mechanisms of syncytium formation and pathogenesis through direct intercellular spread remain. Accordingly, there is a need to provide a new anti-HIV drugs which are not limited to inhibiting reverse transcription as their mechanism of action.
Coumarins and Photoactive Compounds Lomatium suksdorfii (Umbelliferae) is distributed on the United States western coast. The roots of several Lomatium species were used medicinally by the Gosiute Indians who called the plant "pia-a-na-tsu" or "great medicine". The oil and a crystalline substance obtained from L. suksdorfii were previously found to exhibit antispasmodic and antibacterial activities (Pettinate et al, J. Amer. Pharm. Assoc., 48:423 (1959).
Powers et al, in U.S. Pat. No. 5,089.634, disclose isocoumarins with cationic substituents for use in inhibiting serine proteases with trypsin-like, chymotrypsin-like and elastase-like specificity and their roles as anticoagulant agents and anti-inflammatory agents. Isocoumarin and related heterocyclic compounds represented according to disclosed formula (I) or a pharmaceutically acceptable salt are also disclosed.
Gulliya et al, in U.S. Pat. No. 5,177,073, discloses therapeutic compositions derived from a pre-activated photoactive compound and a conveyor for destroying tumor or other pathogenic biological contaminants infecting animal body tissues, wherein the conveyor can be a matrix support or an antibody. The activation of the photoactive compound is used to produce the pre-activated photoactive compound retaining therapeutic activity subsequent to activation. Such photodynamic therapy involves the administration of one or more photoactive agents to a subject to be treated followed by exposing the specific target location or target organ of the subject to light. The photoactive compound is required to have one or more chromophores capable of absorbing light energy and capable of being coupled to a matrix support or antibody.
Call and Green, Proc. Montana. Acad. Sci. 16:49 (1956) describe methods for activation of pyronocoumarin derivatives.
It is well known that one member of a group of steroisomers has very potent activity, while other member(s) of the group may be useless for the same purpose. Often, mixtures of stereoisomers have much lower activity than is useful. For compounds having stereoisomer, it is important to be able to prepare the useful stereoisomer apart from the other stereoisomers, as separation of stereoisomers is often difficult and inefficient.
Sharpless and his co-workers have extensively researched the asymmetric dihydroxylation of olefins since 1988, as reported in Jacobsen et al., J. Am. Chem. Soc., 1988, 110, 1968-1970. Substantial progress has been made in the development of ligands that generate ever higher levels of enantioselectivityz: Crispino et al., J. Org. Chem., 1993, 58, 3785-3786; Amberg et al., J. Org. Chem., 1993, 58, 844-849, Sharpless et al., J. Org. Chem., 1992, 57, 2768-2771. A variety of olefins have been investigated with very good results. Unfortunately, a high level of enantioselectivity in asymmetric dihydroxylation of a styrene-like olefin contained in a six-membered ring fused with benzene has not been reported.
Citation of documents herein is not intended as an admission that any of the documents cited herein is pertinent prior art, or an admission that the cited document is considered material to the patentability of the claims of the present application. All statements as to the date or representation as to the contents of these documents is based on the information available to the applicant and does not constitute any admission as to the correctness of the dates or contents of these documents.